Monday, April 13, 2015
Through prior arrangements with the owner, members of the Baltimore Mineral Society and the Chesapeake Gem and Mineral Society received permission to collect at this "dark limestone" quarry in Middleburg on Saturday, April 11, 2015. We knew it had yielded fluorite and that "cave flowers" had been found on the berms where collecting was permitted,
We determined the fluorite to be easy to find in cubes up to slightly more than an inch.It occurs in veins of dolomite within large boulders of dark limestone. To separate the fluorite cubes from the dolomite encasing them is problematic; likewise to separate the dolomite veins from the limestone through which they intrude. Many of the veins are no more than an inch wide. The preferred method for collecting the fluorite is to whack the large boulders with such veins using a large sledge hammer and trim away as much limestone as possible from the resulting particles
A higtlight of the day was an encounter with aragonite rubble that clearly originated in a cave that had collapsed on a surrounding wall. Unlike the clear to pale orangish brown aragonite stones present on many of the berms, some of this aragonite demonstrated a presence of stalactites, stalagmites, and "cave flowers," The seven inch stalactite at right proved to be one of the day's premier finds along with nodular stalagmic sections and some crumbly aragonite with vugs containing impressive microscopic orangish brown aragonite needles. Since nearly all caves or caverns in the region where such material exists are public places that prohibit collecting, this quarry provided a rare such opportunity, although the picking were slim.
Other finds included magnificent dendrites, pictured at left. Also present, were colorless calcite crystals to about five millimeters as seen at right within vugs occurring in a very few limestone boulders. The only other material of notable interest to be uncovered were mud crack rocks.
Even with permission to also collect at the nearby National Limestone Quarry in Mt. Pleasant Mills, the Middleburg locality sufficed to occupy our group for six hours. With two hours of collecting time remaining, we headed to to the Mt. Pleasant Mills Quarry to a spot that yielded fine barrel-shaped calcite crystals.